Classic/Antique Car Repair: Rough Idle, vacuum leak, wd 40

Question
Dick: I received your response to my last question, and have some additional info. I would like you to have.

I showed your response to the mechanic that services my 1954 New Yorker. He continually advises me, that he feels that there is a "GASKET" leak from the gasket under the carb.

Would this type of a leak cause the problem I am having?

Is there anything I can do, to determine if there is such a leak, short of removing the carb?

I hope I am not inconveniencing you, with so many questions, but you are my only expert source.

Thanking you again for all your help, I remain,

Respectfully,

Anthony J. Vitale # 246

Answer
Yes, there is a gasket between the carburetor and the intake manifold.   If there is a vacuum leak anywhere, it will affect the idle, so that could be the problem.  

The way to determine if there is any vacuum leak without getting fancy is to remove the air cleaner, let the engine idle, and slowly move a piece of cardboard or something similar over the top of the front part of the carburetor in such a way as to partly block off the air flow down into the carburetor.  As you slowly move the cardboard across the opening, listen carefully to the engine idle speed - if at any point you notice you are making the idle speed up, then you have proven that you improve the idle by blocking off some air, this is equivalent to proving that there is too much air getting into the engine, so you have proven that there is a vacuum leak.  

If you want to investigate further, you can take a can of WD-40 and spray it around the base of the carburetor - when you find the leak, the engine will speed up momentarily, because the WD-40 is an excellent source of fuel.  The leak can be almost anywhere, but spray all around the mounting flange of the carburetor as a first step - you might find it right away.  

Your mechanic might have already done all this, or he might just be guessing - you can put your detective badge back on again and check it out for yourself!

Your questions do not bother me at all.  I appreciate someone who is keeping a 51 year old car running - that is what we need in the hobby.

I'm off tomorrow to a car show in Los Angeles (120 miles away) in my 1956 Packard, just to give it some exercise and to spend the day with my wife - a nice way to spend Sunday!

Dick